The research project is designed to establish the significance of dilatations of neurosecretory axons (Herring bodies), the smooth axoplasmic reticulum and the pituicytes (neurohypophysial glial cells) in the secretory activity of peptidergic neurons, the regenerative capabilities of these neurons when their axons are transected at varying distances from the perikarya, and the role which pituicytes play in that process. The fate of 35 S-cysteine labeled neurosecretory granulated vesicles will be studied during and following induced localized arrest of the axoplasmic flow (experimental formation of Herring bodies) at the level of the infundibulum in the frog, and in normal dehydrated, and dehydrated and subsequently rehydrated rats; furthermore acid phosphatase activity and the presence of immunocytochemically demonstrable neurophysin vasopression and oxytocin in the axoplasmic reticulum and its involvement in retrograde transport, as demonstrated with horseradish peroxidase, will be investigated. The significance of Herring bodies will be further investigated through the study of the ontogenetic development of axon dilatations that consistently occur in the rar hypophysial stalk and the effect of colchicine administration on these structures in adult rats. Cell fractionation followed by differential centrifugation, chromatography and electrophoresis will be used for first characterization of proteins in the rough endoplasmic reticulum of pituicytes, obtained from neurohypophyses after complete degeneration o their axons; identical pituicyte preparations will be grafted at varying levels of transection of the neurosecretory axons to test their role in the regeneration of these fibers.